Thailand monsoon deluge disrupts transport and raises flash-flood concerns

A deep low-pressure system and strong southwest monsoon brought heavy rain and widespread flooding across Thailand on 26 September 2026. Forecasts warned of intense downpours continuing into Sunday, with Bangkok and central and eastern regions especially affected. Rough seas in the Gulf of Thailand led officials to advise small boats to remain in port.

Thailand’s weather service placed most of the country under heavy-to-very-heavy rain alerts from 25–27 September. A slow-moving low-pressure area within a monsoon trough concentrated downpours over the central plain and eastern seaboard, where forecasts covered up to 80 percent of localities. Foothill and low-lying communities faced flash-flood and runoff risks, while strong winds and rough Gulf waters kept small upper-Gulf boats advised to stay in port through at least 27 September.

Earlier August and early September warnings noted saturated ground and elevated rivers. Flooding had already hit northern and northeastern provinces such as Chiang Rai, Chiang Mai and Khon Kaen, affecting villages and roads. Renewed rainfall extended the flood season. In Bangkok, all 50 districts were declared disaster-affected, with knee-deep water on some roads, impassable side streets, and longer trips despite operating rail and highway links.

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